|Publication number||US7808255 B2|
|Application number||US 12/061,483|
|Publication date||Oct 5, 2010|
|Filing date||Apr 2, 2008|
|Priority date||Apr 5, 2007|
|Also published as||CN101663638A, CN101663638B, DE112008000906T5, US8624609, US20080246496, US20100321043, WO2008122759A1|
|Publication number||061483, 12061483, US 7808255 B2, US 7808255B2, US-B2-7808255, US7808255 B2, US7808255B2|
|Inventors||Luben Hristov, Peter T Sleeman, Harald Philipp, Esat Yilmaz, Samuel Brunet|
|Original Assignee||Atmel Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (20), Non-Patent Citations (2), Referenced by (52), Classifications (8), Legal Events (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The invention relates to 2-dimensional position sensors. More particularly the invention relates to 2-dimensional position sensors of the type based on capacitive proximity sensing techniques. Such sensors may be referred to as 2-dimensional capacitive transducing (2DCT) sensors. 2DCT sensors are based on detecting a disturbance in a capacitive coupling of sensor electrodes, either to ground or to another electrode, caused by the proximity of a pointing object. A measured location for the disturbance corresponds to a measured position for the pointing object.
2DCT sensors are typically actuated by a human finger, or a stylus. Example devices include touch screen and touch sensitive keyboards/keypads, e.g. as used for controlling consumer electronic devices/domestic appliances, and possibly in conjunction with an underlying display, such as a liquid crystal display (LCD), or cathode ray tube (CRT). Other devices which may incorporate 2DCT sensors include pen-input tablets and encoders used in machinery for feedback control purposes, for example. 2DCT sensors are capable of reporting at least a 2-dimensional coordinate, Cartesian or otherwise, related to the location of an object or human body part, by means of a capacitance sensing mechanism.
Devices employing 2DCT sensors have become increasingly popular and common, not only in conjunction with personal computers, but also in all manner of other appliances such as personal digital assistants (PDAs), point of sale (POS) terminals, electronic information and ticketing kiosks, kitchen appliances and the like. 2DCT sensors are frequently preferred to mechanical switches for a number of reasons. For example, 2DCT sensors require no moving parts and so are less prone to wear than their mechanical counterparts. 2DCT sensors can also be made in relatively small sizes so that correspondingly small, and tightly packed keypad arrays can be provided. Furthermore, 2DCT sensors can be provided beneath an environmentally sealed outer surface/cover panel. This makes their use in wet environments, or where there is a danger of dirt or fluids entering a device being controlled attractive. Furthermore still, manufacturers often prefer to employ interfaces based on 2DCT sensors in their products because such interfaces are often considered by consumers to be more aesthetically pleasing than conventional mechanical input mechanisms (e.g. pushbuttons).
U.S. Pat. No. 5,730,165 describes a capacitive sensing device which relies on measuring the capacitance of a sensing electrode to a system reference potential (earth). The principles described in U.S. Pat. No. 5,730,165 utilize passive capacitive sensing techniques. The contents of U.S. Pat. No. 5,730,165 are incorporated herein in their entirety by reference as background material to the invention. In broad summary, passive capacitive sensors employ sensing electrodes coupled to capacitance measurement circuits. Each capacitance measurement circuit measures the capacitance (capacitive coupling) of its associated sensing electrode to a system ground. When there is no pointing object near to the sensing electrode, the measured capacitance has a background/quiescent value. This value depends on the geometry and layout of the sensing electrode and the connection leads to it, and so on, as well as the nature and location of neighbouring objects, e.g. the sensing electrodes proximity to nearby ground planes. When a pointing object, e.g. a user's finger, approaches the sensing electrode, the pointing object appears a virtual ground. This serves to increase the measured capacitance of the sensing electrode to ground. Thus an increase in measured capacitance is taken to indicate the presence of a pointing object.
U.S. Pat. No. 5,730,165 are primarily directed to discrete (single button) measurements, and not to 2D position sensor applications. However the principles described in U.S. Pat. No. 5,730,165 are readily applicable to 2DCT sensors, e.g. by providing electrodes to define either a 2D array of discrete sensing areas, or rows and columns of electrodes in a matrix configuration.
U.S. Provisional Patent Application 60/803,510, subsequently filed as U.S. patent application Ser. No. 11/752,615 which published as US2006/0279395 on 6 Dec. 2007, describes a 2DCT sensor comprising a substrate with a sensitive area defined by a pattern of electrodes in which the electrodes are sensed by passive sensing techniques. A capacitance measurement circuit of the type described in U.S. Pat. No. 6,288,707, as shown in FIG. 5 of U.S. application 60/803,510, is coupled to the sensing electrodes for determining a change in capacitance caused by the approach of a user's finger or other object to the sensing electrodes. Further details of sensor circuitry and methods of driving the sensor circuitry are available in U.S. Pat. No. 5,730,165 and U.S. Pat. No. 7,148,704. It has been found that there are some limitations associated with 2DCT sensors which operate on passive sensing techniques. For example, passive 2DCT sensors are strongly sensitive to external ground loading. That is to say, the sensitivity of such sensors can be significantly reduced by the presence of nearby low impedance connections to ground which can limit their applicability. For example, some types of display screen technology provide for a low-impedance coupling to ground across the visible screen. This means a passive 2DCT overlaying the display screen will often under-perform because the relatively strong coupling to ground through the screen itself reduces the sensitivity of the 2DCT to any additional coupling to ground caused by an approaching pointing object. A similar effect means 2DCT sensors can be relatively sensitive to changes in their environment e.g., a 2DCT sensor might behave differently according to its location because of differences in capacitive coupling (ground loading) to external objects. 2DCT sensors are also relatively sensitive to environmental conditions, such as temperature, humidity, accumulated dirt and spilt fluids, etc. All of these effect the sensor's reliability and sensitivity. Furthermore, the measurement circuitry associated with passive 2DCT sensing is generally of high input impedance. This makes passive sensors prone to electrical noise pick up, e.g. radio frequency (RF) noise. This can reduce reliability/sensitivity of the sensor and also places constraints on sensor design (e.g. there is limited freedom to use relatively long connection leads/traces between the sensing electrodes and associated circuitry.
Thus, there is a need to develop an improved 2DCT sensor which addresses the above-mentioned problems of certain known 2DCT sensors and particularly those 2DCT sensors which rely on passive capacitive sensing techniques as described in U.S. application 60/803, 510.
According to a first aspect of the invention, there is provided a two-dimensional position sensor comprising a substrate with a sensitive area defined by a pattern of electrodes, the pattern of electrodes including drive electrodes and sense electrodes generally extending in a first direction (hereinafter, the x-direction) and interleaved in a second direction (hereinafter, the y-direction, where the x- and y-directions can be oriented along any axis of actuation, but are generally orthogonally oriented towards each other), wherein the sense electrodes comprise first, second and third groups of elements shaped such that adjacent ones of the elements of the first and second groups co-extend in the x-direction over a portion of the sensitive area and adjacent ones of the elements of the second and third groups co-extend in the x-direction over another portion, and wherein the drive electrodes are arranged to capacitively couple with the sense electrodes.
The 2DCT sensor of the invention uses active capacitive sensing. Active 2DCT sensors have been found to be less prone to the above-mentioned effects associated with passive 2DCT sensors. The active 2DCT sensor of the invention is based on measuring capacitive coupling between two electrodes rather than between a single sensing electrode and a system ground. The principles underlying active capacitive sensing techniques are described in U.S. Pat. No. 6,452,514, the contents of which are incorporated herein by reference. In an active-type sensor, one electrode, the so-called drive electrode, is supplied with an oscillating drive signal. The degree of capacitive coupling of the drive signal to the sense electrode(s) is determined by measuring the amount of charge transferred to the sense electrode by the oscillating drive signal. The amount of charge transferred, i.e. the strength of the signal seen at the sense electrode, is a measure of the capacitive coupling between the electrodes. When there is no pointing object near to the electrodes, the measured signal on the sense electrode has a background/quiescent value. However, when a pointing object, e.g. a user's finger, approaches the electrodes (or more particularly approaches near to the region separating the electrodes), the pointing object acts as a virtual ground and sinks some of the drive signal (charge) from the drive electrode. This acts to reduce the strength of the component of the drive signal coupled to the sense electrode. Thus a decrease in measured signal on the sense electrode is taken to indicate the presence of a pointing object.
An active sensor described in U.S. Pat. No. 6,452,514 comprises drive electrodes extending in rows on one side of a substrate and sense electrodes extending in columns on the other side of the substrate so as to define an array of N by M touch keys. Each key corresponds to an intersection between a drive electrode and a sense electrode. Thus the array of keys described in U.S. Pat. No. 6,452,514 may be termed a matrixed array with a single drive electrode associated with keys in a given row and a single sense electrode associated with keys in a given column. This reduces the number of drive and sense channels required, since a single drive channel simultaneously drives all of the keys in a given row and a single sense channel senses all of the keys in a given column. The capacitive coupling between the electrodes at the positions of the different keys can be determined by driving the appropriate row and sensing the appropriate column. For example, to determine the capacitive coupling between the electrodes associated with a key at the intersection of row 2 and column 3, the drive signal is applied to the drive electrode of row 2 while the sense channel associated with the sense electrode of column 3 is active. The output from the active sense channel reflects the capacitive coupling between the electrodes associated with the key under investigation. Different keys can be scanned by sequencing through different combinations of drive and sense channels. In one mode the drive electrodes may be driven sequentially while the sense electrodes are all continuously monitored. A signal change on one (or more) of the sense electrodes indicates the presence of a pointing object. The sense electrode on which the change is seen defines position in one dimension, the drive electrode being driven when the change was seen defines position in the other dimension.
When implementing drive and sense channel circuitry of the kind described in U.S. Pat. No. 6,452,514 in an integrated circuit (IC) chip package, each drive channel requires one pin-out while each sense channel requires two pin-outs. Thus, for a 2DCT sensor according to the invention comprising an array of n×m sensing areas, a matrixed array requires N+2M pin-outs (or M+2N pin-outs depending on which of the rows and columns are drive or sense electrodes). However, a discrete (non-matrixed array) requires 3 NM pin-outs. Circuit connections, and in particular pin-outs in IC chip implementations, are expensive, both in monetary terms, and in terms of the physical space and complexity required to implement them. Advantageously, the 2DCT sensor of the invention requires only one pin-out for each drive channel and two pin-outs for each sense channel.
The sensor may preferably further comprise a controller comprising a drive unit for applying drive signals to the drive (D) electrodes, and a sense unit for measuring sense signals received from the sense (S) electrodes representing a degree of coupling of the drive signals between the drive electrodes and the sense electrodes. Since sense channels are generally more expensive to implement that drive channels, a cheaper sensor in accordance with the invention can be provided which may employ a controller implemented in an integrated chip requiring fewer pin-outs than known matrixed passive capacitive position sensors.
The controller may preferably further comprise a processing unit for calculating a position for an interacting object from an analysis of the sense signals obtained by applying drive signals to the drive electrodes. The position determination in each axis may include interpolating so that position can be determined. Namely, the processing unit is preferably operable to determine position in the x-direction by an interpolation between sense signals obtained from co-extending pairs of groups of sense electrodes, and position in the y-direction by an interpolation between sense signals obtained from different sequences of drive signals applied to the drive electrodes.
The electrodes can be made of a transparent material, such as indium tin oxide (ITO), Orgacon™ or any other suitable material. The substrate can also be made of a transparent material, such as glass or a transparent plastics material, e.g. a polymethyl methacrylate (PMMA) such as Perspex, Polyethylene Terephthalate (PET), a polycarbonate (PC) such as Lexan™, or a cycloolefin copolymer (COP) such as Zeonor™ or Topas™. However, in some applications, it may be the case that the electrodes and/or the substrate are opaque e.g. metal electrodes on opaque plastic, to create a mouse pad or track pad for example.
The groups of sense electrodes which co-extend can have complementary tapers over their distance of co-extension to provide ratiometric capacitive signals. Alternatively, the elements of respective groups of sense electrodes which co-extend have adjacent blocks of varying area over their distance of co-extension to provide ratiometric capacitive signals. The sense electrodes may be structured in a variety of topographical forms in order to provide the co-extension. For example, the drive and sense electrodes may interdigitate in order to provide said capacitive coupling. Over the sensitive area, the drive and sense electrodes are advantageously formed of conductive material which does not exceed a feature width substantially smaller than a characteristic spacing in the y-direction between adjacent rows of drive electrodes, such as 2, 3, 4, 5, 6, 7, 8, 9 or 10 times smaller. This keeps the amount of conductive material low while providing a large amount of capacitive coupling, which has benefits for noise reduction and signal strength.
In preferred embodiments, the elements of at least one of the first and third groups of sense electrodes form two sections separated in the y-direction by a channel, and wherein the elements of the second group of sense electrodes are externally connected to the sense unit through conductive traces that pass through the channels to a side of the sensitive area. This type of arrangement, which can also be applied to further groups of sense electrodes if provided, ensures that the conductive traces leading to inner ones of the sense electrode groups do not pass between paired drive and sense electrodes of peripheral ones of the sense electrode groups. The reduction in their capacitive coupling that would otherwise occur is thus avoided.
If there are at least three groups of sense electrodes externally connected to the sense unit through one side of the sensitive area, referred to as peripheral, intermediate and inner sense electrodes, it is advantageous if the elements of the inner sense electrodes are externally connected to the sense unit through conductive traces which become progressively wider in the y-direction from said one side towards the elements of the inner sense electrodes. This reduces the resistance of the path to the inner sense electrode groups and avoids reduction in sensitivity for such groups. For example, the elements of the peripheral and intermediate sense electrodes can form two sections separated in the y-direction, wherein the two sections of each element of the intermediate sense electrodes are externally connected to the sense unit through respective conductive traces that pass between the two sections of the peripheral sense electrodes to said one side of the sensitive area and leave a channel therebetween, and wherein the elements of the inner sense electrodes are externally connected to the sense unit through conductive traces that pass through the channel formed between the sections of the peripheral and intermediate sense electrodes.
It can also be advantageous if the elements of at least one of the groups of sense electrodes are hollow in the plane of the sensitive area. This is one way of reducing conductive material which does not contribute significantly to capacitive coupling with the drive electrodes. Other measures are also possible, such as through interdigitation and use of line-based electrode forms having a small feature width as referred to above.
It will be understood that the position of an object is defined by an appropriate coordinate system, most commonly an xy Cartesian system in which they are orthogonal, although they may be at a non-orthogonal angle. Moreover, in the following there is reference to x- or horizontal and y- and vertical respectively for convenience, although this implies no particular alignment to real space, such as relative to the direction of gravity.
According to a second aspect of the invention there is provided a control panel incorporating a two-dimensional position sensor according to the first aspect of the invention.
According to a third aspect of the invention there is provided an apparatus having a control panel incorporating a two-dimensional position sensor according to the first aspect of the invention.
According to a fourth aspect of the invention there is provided a method of sensing position of an actuation on a sensitive area of a two-dimensional position sensor, the sensitive area being defined by a pattern of electrodes including drive electrodes and sense electrodes, both generally extending in a first direction, hereinafter the x-direction, and interleaved in a second direction, hereinafter the y-direction, wherein the sense electrodes comprise first, second and third groups of elements shaped such that adjacent ones of the elements of the first and second groups co-extend in the x-direction over a portion of the sensitive area and adjacent ones of the elements of the second and third groups co-extend in the x-direction over another portion, and wherein the drive electrodes are arranged to capacitively couple with the sense electrodes, the method comprising: applying drive signals to the drive electrodes; measuring sense signals received from each group of the sense electrodes representing a degree of capacitive coupling of the drive signals between the drive electrodes and each group of the sense electrodes; determining position in the x-direction by an interpolation between sense signals obtained from co-extending pairs of groups of sense electrodes; and determining position in the y-direction by an interpolation between sense signals obtained from different sequences of drive signals applied to the drive electrodes.
For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example to the accompanying drawings.
The electrode pattern 30 on the substrate 40 can be provided using conventional techniques (e.g. lithography, deposition, or etch or deactivation techniques). The substrate is of a dielectric material such as a plastics film, in this case Polyethylene Terephthalate (PET). The electrodes comprising the electrode pattern are of a transparent conductive material, in this case Indium Tin Oxide (ITO). Alternatively, the electrodes could be formed from an opaque conductive material such as metal e.g. copper. The substrate may be bonded to an overlying panel (not shown) using a suitable pressure sensitive adhesive (PSA) which can be clear to allow light transmission. Thus the sensitive area of the sensor as a whole is transparent. If transparent, the sensor layer may be used over an underlying display without obscuration. In other embodiments, if the sensor layer is opaque, it may comprise a conventional printed circuit board or other substrate with a copper electrode pattern, e.g. for use in a mobile telephone keypad.
The controller 20 provides the functionality of a drive unit 12 for supplying drive signals to portions of the electrode pattern 30, a sense unit 14 for sensing signals from other portions of the electrode pattern 30, and a processing unit 16 for calculating a position based on the different sense signals seen for drive signals applied to different portions of the electrode pattern. The controller 20 thus controls the operation of the drive and sense units, and the processing of responses from the sense unit 14 in the processing unit 16, in order to determine the position of an object, e.g. a finger or stylus, adjacent the sensor 10. The drive unit 12, sense unit 14 and processing unit 16 are shown schematically in
As shown in
As shown in
The sensor 10 of the invention therefore comprises a plurality of driven electrodes and a plurality of sense electrodes comprising a network of interconnected electrodes across the sensitive area of the sensor. Each neighbouring pairing of a drive element and a sense element may be considered to correspond to a discrete sensor area which may be operated according to the techniques described in U.S. Pat. No. 6,452,514. In use, the position of an object is determined in a measurement acquisition cycle in which the bar electrodes 52 are sequentially driven by respective drive channels and the amount of charge transferred to the sense electrodes from each bar electrode is determined by the sense channels.
The drive channel associated with the presently driven electrode 100, the sense channel associated with sense electrode 104 and elements of the sensor controller are shown as combined processing circuitry 400 in
It will be understood that the circuit element designated as 402 provides a charge integration function that may also be accomplished by other means, and that this type of circuit is not limited to the use of a ground-referenced capacitor as shown by 402. It should also be self-evident that the charge integrator 402 can be an operational amplifier based integrator to integrate the charge flowing through in the sense circuitry. Such integrators also use capacitors to store the charge. It may be noted that although integrators add circuit complexity they provide a more ideal summing junction load for the sense currents and more dynamic range. If a slow speed integrator is employed, it may be necessary to use a separate capacitor in the position of 402 to temporarily store the charge at high speed until the integrator can absorb it in due time, but the value of such a capacitor becomes relatively non-critical compared to the value of the integration capacitor incorporated into the operational amplifier based integrator.
It can be helpful for the sampling switch 401 to connect the sense electrode of the sensor to ground when not connected to the charge integrator 402 during the changes of drive signal of the chosen polarity (in this case positive going). This is because this can create an artificial ground plane, thus reducing RF emissions, and also, as noted above, permitting the coupled charge of opposite polarity to that being sensed by the charge integrator 402 to properly dissipate and neutralize. It is also possible to use a resistor to ground on the sense electrode to accomplish the same effect between transitions of drive channels 101. As an alternative to a single-pole double-throw (SPDT) switch 401, two independent switches can be used if timed in an appropriate manner.
As described in U.S. Pat. No. 5,730,165, there are many signal processing options possible for the manipulation and determination of a detection or measurement of signal amplitude. U.S. Pat. No. 5,730,165 also describes the gain relationship of the arrangement depicted in
The drive channel may be a simple CMOS logic gate powered from a conventionally regulated supply and controlled by the sensor controller 20 to provide a periodic plurality of voltage pulses of a selected duration (or in a simple implementation a single transition from low-to-high or high-to-low voltage, i.e. a burst of one pulse). Alternatively, the drive channel may comprise a sinusoidal generator or generator of a cyclical voltage having another suitable waveform. A changing electric field is thus generated on the rising and failing edges of the train of voltage cycles applied to the driven electrode. The driven electrode and the sense electrode are assumed to act as opposing plates of a capacitor having a capacitance CE. Because the sense electrode is capacitively coupled to the driven electrode, it receives or sinks the changing electric field generated by the driven column electrode. This results in a current flow in the sense electrode induced by the changing voltage on the driven electrode through capacitive differentiation of the changing electric fields. The current will flow towards (or from, depending on polarity) the sense channels in the sense unit 14. As noted above, the sense channel may comprise a charge measurement circuit configured to measure the flow of charge into/out of (depending on polarity) the sense channel caused by the currents induced in the sense electrode.
The capacitive differentiation occurs through the equation governing current flow through a capacitor, namely:
where IE is the instantaneous current flowing to the sense channel S and dV/dt is the rate of change of voltage applies to the driven electrode D1. The amount of charge coupled to the sense electrode (and so into/out of the sense channel S) during an edge transition is the integral of the above equation over time, i.e.
Q E =C E ×V.
The charge coupled on each transition, QE, is independent of the rise time of V (i.e. dV/dt) and depends only on the voltage swing at the driven electrode (which may readily be fixed) and the magnitude of the coupling capacitance CE between the driven electrode and sense electrode. Thus a determination of the charge coupled into/out of charge detector comprising the sense channel in response to changes in the drive signal applied to the driven electrode is a measure of the coupling capacitance CE between the driven electrode and the sense electrode.
The capacitance of a conventional parallel plate capacitor is almost independent of the electrical properties of the region outside of the space between the plates (at least for plates that are large in extent compared to their separation). However, for a capacitor comprising neighbouring electrodes in a plane this is not the case. This is because at least some of the electric fields connecting between the driven electrode and the sense electrode “spill” out from the substrate. This means the capacitive coupling (i.e. the magnitude of CE) between the driven electrode and the sense electrode is to some extent sensitive to the electrical properties of the region in the vicinity of the electrodes in to which the “spilled” electric field extends.
In the absence of any adjacent objects, the magnitude of CE is determined primarily by the geometry of the electrodes, and the thickness and dielectric constant of the sensor substrate. However, if an object is present in the region into which the electric field spills outside of the substrate, the electric field in this region may be modified by the electrical properties of the object. This causes the capacitive coupling between the electrodes to change, and thus the measured charge coupled into/from the charge detector comprising the sense channel(s) changes. For example, if a user places a finger in the region of space occupied by some of the of the spilled electric fields, the capacitive coupling of charge between the electrodes will be reduced because the user will have a substantial capacitance to ground (or other nearby structures whose path will complete to the ground reference potential of the circuitry controlling the sense elements). This reduced coupling occurs because the spilled electric field which is normally coupled between the driven electrode and sense electrode is in part diverted away from the electrode to earth. This is because the object adjacent the sensor acts to shunt electric fields away from the direct coupling between the electrodes.
Thus, by monitoring the amount of charge coupled between the driven electrode and the sense electrode, changes in the amount of charge coupled between them can be identified and used to determine if an object is adjacent the sensor (i.e. whether the electrical properties of the region into which the spilled electric fields extend have changed).
The two-dimensional position sensor or touch screen sensor of the invention therefore relies on active capacitive sensing techniques as opposed to passive capacitive sensing techniques which provides for a more optimal determination of position of an object, greater linearity of output signal as an object moves over the sensor, and greater sensitivity of the sensor to capacitive changes caused by an approaching object. In addition, as previously described, the sensor of the invention is more versatile and less affected by ground loading compared to known sensors.
As previously described, the sensor of the invention operates on matrix sensing principles described in U.S. Pat. No. 6,452,514. Such matrix sensing involves capacitive field changes between two electrodes, a drive electrode and a sense electrode, rather than determination of a change in capacitance from a sensing electrode to a reference potential (e.g. ground). Such matrix sensing in the touch screen sensor of the invention involves capacitive e-fields which are more “closed” compared to capacitive e-fields in passive sensors which are typically more “open”. This improves the capacitive sensitivity of the sensor.
The x position of the touch or other actuation is obtained by ratiometric interpolation of the signal strength of the two groups of the three groups of sense electrodes S1, S2, S3 that have the two strongest signals.
The y position of the touch or other actuation is also obtained by ratiometric interpolation of the signal strength, but in a somewhat different way. Once the full set of 6 signals is collected from the six drive events at t1-t6, the two adjacent events that yielded the strongest signals are selected, and the y position determined by ratiometric interpolation of the signal strength of these two signals. For example, if the strongest pair of adjacent signals is obtained from the driving of channels D2 and D3, and the signal obtained when driving D2 is two times greater than the signal obtained when driving D3, then the touch is determined to have taken place ⅓ of the way from the D2 drive electrode towards the D drive electrode.
The sensors of the invention may comprise more than three or four groups of sense electrodes depending on the design of the sensor. Five or more groups of sense electrodes may be present for example if the width of the electrode pattern is increased in the x-direction to accommodate a larger-size capacitive sensor. For example, the sensors described below and illustrated in
The electrode patterns described in co-pending U.S. Patent Application 60/803,510 and its subsequent regular filing U.S. Ser. No. 11/752,615 which was published as US2006/0279395 are incorporated herein by reference. The electrode patterns of U.S. Patent Application 60/803,510 are similar to the electrode patterns described hereinabove and such patterns can be used to measure capacitance based on active capacitive sensing techniques in accordance with the invention described above, although not optimised for such.
It will be appreciated that the sensor of the invention is applicable to many types of device/appliance. For example, sensors can be used with ovens, grills, washing machines, tumble-dryers, dish-washers, microwave ovens, food blenders, bread makers, drinks machines, computers, home audiovisual equipment, personal computers, portable media players, PDAs, cell phones, computers, games consoles and so forth.
More generally the invention may be used in conjunction with any appliance having a human-machine interface. It is also possible to provide a sensor similar to those described above which is provided separately from a device/appliance which it may be used to control, for example to provide an upgrade to a pre-existing appliance. It is also possible to provide a generic sensor which may be configured to operate a range of different appliances. For example, a sensor may be provided that has programmable keys which a device/appliance provider may associate with desired functions by appropriately configuration, for example by reprogramming.
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|U.S. Classification||324/686, 345/174, 324/660, 324/662|
|International Classification||G01R27/26, G06F3/045|
|Nov 14, 2008||AS||Assignment|
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